The present invention relates to a DC/DC converter or power supply with improved stability of the output signal. More specifically, the invention relates to a DC/DC converter.
DC/DC converters are well-known. Said known converters are associated to a feedback comparator so as to provide stability to the output signal. The feedback comparator is controlled to switch-over the device as soon as the output voltage exceeds a voltage corresponding to the sum of the reference voltage and an admissible voltage variation or ripple, said admissible voltage variation being as low as possible.
This leads to a too slow working of the comparator, to a large minimum duty cycle and to disturbances at light loads.
The present invention relates to a DC/DC converter or power supply enabling a rapid working of the comparator, while keeping the ripple or admissible voltage variation as low as possible, whereby reducing or preventing disturbance problems at light loads.
The DC/DC converter or power supply of the invention is a converter or power supply comprising a switched-mode regulator, which is provided or associated to a feedback comparator of a feedback voltage for improving the stability of the output signal.
The DC/DC converter or power supply of the invention is further provided with or associated to a means for adding an offset voltage (positive or negative, preferably positive during a voltage increasing mode) to the feedback voltage during at least one phase of the switched-mode regulator or during a portion of at least one phase.
Advantageously, the means for adding an offset voltage is adapted for adding a fixed offset voltage during only one phase of the switched-mode regulator or a portion of said phase.
Preferably, the converter or power supply has means for detecting when a feedback voltage is higher than the sum (reference voltage+admissible voltage variation). In the converter or power supply of the invention, the feedback comparator detects the voltage difference between the sum (feedback voltage+offset voltage) and the reference voltage, and determines whether said difference is at least equal to, advantageously higher than, a voltage value or a numerical voltage value corresponding to an admissible voltage variation. In said embodiment, the means for adding an offset voltage is adapted for adding an offset voltage having a voltage value higher than the admissible voltage variation or having a numerical voltage value higher than the admissible voltage variation. The numerical value of the offset voltage is preferably comprised between 1 and 10 times the numerical voltage value of the admissible voltage variation, most preferably between 1, 5 and 3 times the numerical voltage value of the admissible voltage variation.
For example, the means for adding an offset voltage is adapted for adding an offset voltage having a voltage value equal to or higher than twice the admissible voltage variation or having a numerical voltage value equal to or higher than twice the admissible numerical voltage variation.
According to specific embodiments, the means for adding an offset voltage is adapted for adding said offset voltage during the mode of the regulator corresponding to a voltage increase mode or a portion thereof and/or for adding a negative offset voltage during the mode of the regulator corresponding to a voltage decrease mode or a portion thereof.
The invention relates also to an electronic device comprising at least one converter or power supply of the invention.
The invention further relates also to a method for improving the stability of a signal of an output signal by means of a regulator receiving a signal from a feedback comparator for a feedback voltage with respect to a reference voltage. In said method, an offset voltage is added to the feedback voltage during at least one phase of the switched-mode regulator or a portion of said phase. The feedback comparator determines the difference between the sum (feedback voltage+offset voltage) and the reference voltage, whereby increasing the reaction speed of the comparator.
Advantageously, a predetermined offset voltage is added to the feedback voltage during only one phase of the switched-mode regulator or a portion thereof.
The feedback voltage has a maximum or minimum allowed voltage value corresponding to the sum of the reference voltage with an admissible voltage variation.
Preferably, an offset voltage having a voltage value at least equal to (advantageously higher than) the admissible voltage variation or having a numerical voltage value at least equal to (advantageously higher than) the admissible voltage variation is added to the feedback voltage during one phase of the switched-mode regulator or a portion thereof.
According to an embodiment of the method of the invention, an offset voltage having a voltage value at least equal to (preferably higher) than twice the admissible voltage variation or having a numerical voltage value at least equal to (preferably higher than) twice the numerical admissible voltage variation is added to the feedback voltage during one phase of the switched-mode regulator or a portion of said phase.
According to a detail of an embodiment, an offset voltage is added to the feedback voltage during the voltage increase mode of the regulator or a portion of said phase and/or a negative offset voltage is added to the feedback voltage during the voltage decrease mode of the regulator or a portion of said phase. Said offset voltage and negative offset voltage can have the same numerical value or different numerical value.